Two years ago, while visiting his family in the Russian region of Dagestan, Tamerlan Tsarnaev, the prime suspect in last week’s Boston Marathon bombings, was flagged as a potential extremist by Russian security services. The only evidence they had were his regular visits to a mosque that gets more than its share of attention from police. Since its construction in 2000, the mosque’s broad, emerald-colored dome has been the center of the region’s Salafi community, which adheres to a more orthodox brand of Islam and, over the years, has been a hangout for men killed in shootouts with Russia’s counterterrorism forces.

According to a source close to the Russian security services who specializes in religious radicalism, Tsarnaev attended services at the mosque on Kotrova Street during both of the extended visits he made to Dagestan over the past two years. That is why Russia’s Federal Security Service, the agency better known as the FSB, sent a warning to the FBI in 2011 to be aware of Tsarnaev’s possible links to extremism.

In a statement on April 19, the FBI said it had received information from an unidentified “foreign government” that Tsarnaev was “a follower of radical Islam and a strong believer, and that he had changed drastically since 2010 as he prepared … to join unspecified underground groups.” In response, the FBI said it interviewed Tsarnaev and checked its records for relevant information, but “did not find any terrorism activity, domestic or foreign.”

According to the source in the regional capital of Makhachkala, who spoke to TIME on Monday, Tsarnaev was monitored by Russian counterterrorism forces for at least one month in 2011 and throughout his six-month stay in Dagestan last year. “There wasn’t enough time [in 2011] to come to any conclusions about the extent of his involvement [in Islamist extremism],” the source says, asking to remain anonymous due to the sensitivity of the matter. “So we asked our American colleagues to follow up.”

His account was corroborated by a source close to the FSB in the city of Khasavyurt, the second largest city in Dagestan, who spoke to TIME on Sunday. “It didn’t take much for him to raise suspicion,” the Khasavyurt source said of Tsarnaev, also insisting on anonymity. “Showing up at a Salafi mosque was enough.”

There is no indication that Tsarnaev, who was killed in a standoff with Boston police on Friday, was instructed or pushed toward committing any terrorist acts during his visits to the mosque on Kotrova Street. The vast majority of the mosque’s congregants likely have no connection to the region’s extremist activity, and more moderate Muslims regularly attend services there. Both of TIME’s sources said the Russian security services never observed Tsarnaev make contact with any of the known insurgent leaders or suspected terrorists who operate in Dagestan. But the sermons he heard at the mosque might have contributed to his gradual radicalization, the sources said. “The idea that America and Israel are the axis of evil is pretty typical there. He would have heard some of that,” said the source in Makhachkala. He added, however, that the extremist videos he watched online could also have been an important factor.

On his YouTube channel, which he opened about a month after returning to Boston from a six-month visit to Dagestan last year, Tsarnaev shared the propaganda videos of several radical Islamists, including an insurgent leader who goes by the nom de guerre Abu Dudzhan and hails from the town of Kizilyurt in central Dagestan. “It is just as likely that he was converted [to radical Islam] online as on Kotrova Street,” says the source in Makhachkala. (Some reports claim Abu Dudzhan was killed in a firefight last year, though reports of a militant’s demise in the North Caucasus are all too often premature.)

Tsarnaev’s apparent choice to attend services on Kotrova Street seems to have been part of his religious divergence from his family. Although his mother has said she also became more devout in recent years, the security source in Makhachkala said she was never seen at the Kotrova Street mosque, which generally holds services for men only. The family’s neighbors in Dagestan told TIME over the weekend that Tsarnaev’s father, Anzor, attended services at the more moderate main mosque in Makhachkala, on Dakhadaev Street.

The mosque on Kotrova Street has been one of Russia’s most enduring outposts of Salafi Islam, whose adherents around the world call for strict Shari‘a to govern their societies. Before its construction, smaller Salafi mosques were regularly closed down for extremism in Russia’s predominantly Muslim region of the North Caucasus, which includes Dagestan and neighboring Chechnya. “They would chase us out of one place, and we would congregate in another,” says Magomedtagir Temirchiev, a local devotee of Salafi Islam who helped build the mosque on Kotrova Street in 2000. Its construction was led by a local religious leader named Nadirshakh Khachilaev, who was elected to represent Dagestan in the Russian federal parliament, the State Duma, in 1996. Khachilaev was the leader of the Russian Union of Muslims, which the Ministry of Justice in 2002 deemed as an extremist organization, soon after Khachilaev was charged with orchestrating an ambush on a Russian military convoy in Dagestan. Khachilaev denied those charges. But the case never made it to trial, because Khachilaev was killed in a drive-by shooting outside his home in Makhachkala the following August.

The mosque on Kotrova Street remains at the core of his legacy. It is known in Dagestan either as the Khachilaev Mosque or the Laksky Mosque, after Khachilaev’s ethnic group, the Laks. He is treated as a martyr by many of its congregants, some of whom have also carried on his tendency toward confrontations with the Russian state. “I would be lying if I told you that everyone who gathers there is an angel,” says Temirchiev, one of the usual suspects for counterterrorism forces in Dagestan. “Whenever something blows up, they drag me in for questioning,” he says, his long grey beard making him look much older than his 46 years.

One of the regulars at the mosque on Kotrova Street was Murad Lakhiyanov, one of the most famous leaders of the Islamist underground in Dagestan. In October 2005, police cornered him in a Makhachkala apartment, and after an eight-hour gun battle that included mortar fire from both sides, he was killed. By then, the mosque had already gained infamy as a haunt for local terrorists. In 2002, an explosion ripped through a May Day military parade in the Dagestani town of Kaspiysk, killing 44 people, including 12 children, and wounding 133 others. A manhunt then began for a handful of suspects, some of whom turned out to be regulars at the mosque on Kotrova Street.

Six months later, one of the suspects, Murad Abdurazakov, was found hiding in Temirchiev’s home in Makhachkala. Temirchiev, who spoke to TIME on the terrace of a Makhachkala café just down the street from the mosque he helped build, was sentenced in 2003 for abetting terrorism and served the next six years in the Shamkhal Colony, a high-security prison in Dagestan where many convicted terrorists are held. After his release, he spent time in Moscow and St. Petersburg before returning to Dagestan in the fall of 2012, so he would not have been there at the same time as Tsarnaev. “But I know that our numbers have grown in proportion to the pressure against us,” he says. “Inshallah, they will continue to grow.”

These days, the mosque on Kotrova Street is being expanded. Young men with long beards and skullcaps, the typical accessories of Salafis in Dagestan, have been busy paving the walkway to a new wing of the mosque that is currently under construction. None of the young men working on the project over the weekend said they had ever seen Tsarnaev, but they were not particularly shocked by what he allegedly did in Boston. “Look at what Americans have done in Afghanistan and Iraq,” said one of the men, who would only reveal his first name, Abdullah. “Muslims around the world need to defend each other. That is our belief. So first look at all the Muslim women and children America has killed around the world, and then think about what happened in Boston.”

OLD NEWS......SAY AGAIN....OLDNEWS.......THE RUSSIAN SECURITY SERVICE MADE THIW KNOWN TO THE FBI MANY MOONS AGO.....WHAT DID WE DO ABOUT IT........NADA......NYET......NOTHING.......THEREFORE THE ...BOMBINGS.

Notheing matches the counter-intelligence division of the CHEKA/NKVD/KGB, M16 LONDON WORLD WAR II, .......

I am Confused About Something in the middle East oil countries they have the best colleges and universities in the world because of their oil money, (( all education over there is provided to them for FREE; if students are a Muslim From Another Country the cost is much less than a U.S. education )) So why do they come over here ?

They have the very same courses they are taking over here, and in many cases taught by U.S. professors or middle east professors taught over here.

Could it be our Colleges and Universities they are Recruiting students from Rich Prominent Middle East Families , could it be They Like OIL Money.

U.S. Colleges and Universities Could Not Care Less, If there are some Te****ists , as long as they have Money.

@DaleSmith Mainly due to the fact that the amount of college capacity is sorely lacking as opposed to the demand. For example, while most people can name the Ivy League schools in the United States, very few can name the 1000+ local,regional, and religious institutions that educate the overwhelming majority of students. Most foreign countries lack the capacity of these less well known schools and thus send their students into the United States, England, Australia and other countries with more robust systems.

The reason there are so many radical Muslims is that Islam and Muslims promote, protect and glorify Jihad and violence. Granted there are moderate Muslims, but they are few and seen by other Muslims as traitors! for 1400 Islam has not been peaceful ask any minority, women and gays leaving in a Muslim country. Islam can't live side by side modernity, justice and democracy. There are many Muslim countries, not one is real democracy (Turkey used to be because Ataturk eliminated / controlled radicals, but now they are in power again)

Note there are a lot of "radical" Mosques here -50% have Imams from the Middle East, which is a key reason why a USA Today poll showed 5% of America's Muslims believe violence against the USA is justified. What really bothers me is that none of them I've heard of have issued a "fatwa" (religious condemnation) of bin Laden, other al-Qaeda or Taliban leaders, or other Muslim terrorists. The Imams in Spain and some other nations have done so. Why haven't the American Muslim leaders spoken out so strongly?

None of the young men working on the project over the weekend said they
had ever seen Tsarnaev, but they were not particularly shocked by what
he allegedly did in Boston. “Look at what Americans have done in
Afghanistan and Iraq,” said one of the men, who would only reveal his
first name, Abdullah. “Muslims around the world need to defend each
other. That is our belief. So first look at all the Muslim women and
children America has killed around the world, and then think about what
happened in Boston.”

No they don't hate us or want to kill us, nope, not even saying it out loud can make some people believe it, but there it is people. Just read

@LeeJones Indeed, but look at it from their (the person quoted in the article you cited) perspective, the CIA has been indiscriminately killing bystanders along with low-level targets with drone strikes for years now (Pakistan, Afghanistan) with the blessing of the Pakistani government, and doesn't seem to be slowing down it's activities in any appreciable way. With no other recourse some of the witnesses and families of the dead will be radicalized, and driven to acts of revenge. With the increasing solidarity and galvanization of the world-wide Muslim community you will see increased reprisal attacks launched by people who have not been directly wronged, but feel strong enough empathy for fellow Muslims being attacked to lash out at the United States and any of her allies that support her politics.

So they the author points out that its not an extreme mosque in one paragraph then uses a couple more to explain it was founded by an extreme islamic group. It is obvious their religious views influenced their actions. Why are we trying to pretend there is no connection?

The Islamist are correct, Islam is under attack, Their people have seen that there is life out there. Religious hatred need to be. That reallyscares the clerics, their followers might adopt the 16th century a 6 hundred year leap. Why islam hated women is beyond understanding, after all, all men have to by necessity had a mother. Comments like the one from the Iranian president, that women cause earthquakes are a peek into the Islamist psyche. Granted over the years I have had women who have not only rocked my world, but rung my chimes , blown my whistle, so there is something to that statement. But, the real insight is that basically Islam is a relegion for men who hate women ! Why, because they (The Men) cannot be women.

Interesting attitude on the part of the Muslim community in that region. Maybe I'm wrong, but didn't the US go to bat for the Chechnyan side (the Muslims), and as a result managed to create a rift between the Russian government and our own? In fact, if memory serves me correctly, the US was on the Muslim side in the Bosnian conflict as well. Interesting how these acts are forgotten. I'm betting Putin is gloating over the Boston bombing, hoping the US finally sees the radicals for what they are.

The Russian security people seem to be way more 'heads up' than our own FBI. I hope some heads roll over their failures to follow up on what has to be a flashing red neon sign to monitor the elder Chechen. His return trip to terror central Chechnya and violence and postings and all the other stuff should have alerted (alert being the key word) someone. AFTER the bombing how...how...did he not pop up as a suspect ?

Gee, anyone know any radicals locally that could have pulled off this rather sophisticated Al Queada copyrighted terrorist bombing ? How about the Chechens that the Ruskies told us about...they just live a mile away...been posting terrorist stuff all over the place...grew the terror beard ????. How ironic the FBI agent telling the public that someone out there knows who these guys were...yeah...duh...the clowns in your own office interviewed them !!!! What no photos to match with those big broken noses on the Chechens faces ??? Makes you wonder if these Chechens didn't pull a Whitey Bulgar with the feebles.

"So first look at all the Muslim women and children America has killed around the world, and then think about what happened in Boston.”

Big difference - Any women and children killed by Americans were a mistake. An accident. Unintentional. Islamist bombers and specifically in this case, will stand directly beside women and children and set down a bomb with the full intention of killing them. It's this kind of failed logic that is needed to fuel the fire. My religion is about Love..., so I must kill you. Sad.

@rooney5432 A mistake is not knowing that there are non-targets in the vicinity of the target, to not care that there are non-targets in the vicinity and launch anyway is not a mistake, it is intentional disregard for human life.

@jbrown8970@rooney5432That is like saying someone who steals money is the same as someone who works for it because in the end they both have money. Achieving the same result does not evidence equality.

@pauls15 Not all Mosque are the same, although it is sometimes hard to distinguish between the radical and liberal mosques from the out side, but a good gauge can be the flow of money. The Saudi's are the largest followers of this Salafi (wahabi sect), which is responsible for 99% of the terrorist activities in the name of Islam. This message is spread with the help of generous donations from Saudi's (all over the world). If the majority of the mosque is funded by Saudi's, we should close that mosque or at least keep an eye on its members.

2nd keep an eye on the Saudi/wahabi Imams, that is there 2nd modus operandi , they plant a Wahhabi Mullah in the mosque (who usually get the salary from some Saudi fund/donation) and start preaching hatred and slowly poisoning the well (they call it awakening the Umahh--lame) some of the gullible/troubled or looser/misfit teens or men get easily influenced by this and get radicalized, and they start blaming their failures on everyone.....which for some eventually end in either a terrorist activity or a thawed plot (if the authorities get a wind of it)

What I don't understand is why does our government still allows these Wahhabi Mullahs to come in USA and open up these mosques, are they scared of upsetting the Saudi's?

@ak1127@pauls15 We allow these people to come in because we are Americans and we believe people are innocent till proven guilty. Having said that, I think our intelligence community should know who these people are and we shouldn't allow them in country.

@DebbieHanrahan Debbie, you probably should have cited a domestic terrorist like Timothy McVeigh, Terry Nichols or the Unibomber. McVeigh and Nichols were identified as Christian although Ted (Unibomber) I think was sort of agnostic. I understand your basic point but it doesn't apply compared to these guys I mentioned. Although I agree WBC is a bunch of stupid mumpy fumps.

Those jokers at Westboro are disgusting BUT they're not blowing up 8 year olds. After the London subway bombings a survey showed approximately 25% of the British Muslims believed there was justification for the murders. What percentage of Christians do you think support Westboro ? Too tiny to count. If Westboro bombed innocent people the % would be microscopic. difference is pretty obvious..even Bill Maher made this point the other day

@DebbieHanrahan this will be the first (and only time) I defend the WBC, they use law and non-violent protests to get their point across. Is it despicable the words they use? yes yes it is, but I don't believe any violent acts have ever been attributed to them. That said what they stand for is disgusting but they have not committed any criminal act much less murder.

@DebbieHanrahan
I would love to understand the point of you saying what you just said,
are you arguing with the fact that almost all terror committed world
wide is somehow linked to radical islam? I mean I understand youd like
to have people say "awww look debbie is so sweet" but by not condemning
radical islam you are spitting on the graves of millions of people who
died because of it, kindly set aside your need to be politically correct
and respect the victims. Thanks

@antonmarq Now that you mentioned Walmart, I have to agree here. Walmart without a doubt "has been a hangout for men killed in shootouts" among other things. It seems the cult of Walmart is not doing well by our society.

It should be noted that the explosion in West Texas killed more people & was willingly done in the name of profit, yet not covered and the CEOs are not being held accountable for the murders/homicides they committed

Follow the money! Why there is no conversation about the
Saudi/Gulf Arab money in financing Wahhabi/Salafi/radical
Islamist ideology in central Asia, Pakistan, Iraq, Syria, and elsewhere. After
all, radicalization of Chechen happened with Saudi money. It is time to
recognize that Radical Islam/Salafi/Wahhabi are angry at modernity

@green_fox55 Good analysis. But the flow goes like this. Saudi Wahabbi to Taliban to Chechnya. Many Uigher, Chechens, Kazaks get arrested in AFPAK war. This act was in response to Sunni, Salafist hatred of America. The Shia are considered heritics by Wahabbi's and Salafist. If your intererested in source matl try Strategypage.com

This whole thing is playing out as one big cover up, the more that comes out the more the FBI and the rest had to know, something is very wrong here. And this country needs to close it's boarders to these Dangerous "religious" groups, they teach hate and destruction if they don't like what one believes.

@alienstarship That is one broad brush you are using. All Muslim's are not bad. The Muslim community can and should do more to frown upon this type of thing, but we see signs they are moving in that direction. Having a sermon about a Christian Martin Luther King is a great example. The "bad" Muslim jumped up and was very upset. We need more moderation in the Muslim community and many are trying.

What we don't need is to step all over our religious freedom's and cause even more hate. And I'm an athiest. I just believe in letting people practice their religion.